This invention relates to a modular charging device for use in printing and imaging systems. More particularly, the present invention relates to a modular charging device wherein a plurality of charger units are arranged together in a modular fashion. Such a modular charging device is useful in a wide variety of printing and imaging processes, such as in migration imaging, electrostatographic imaging, ionographic imaging, and the like.
A wide variety of printing and imaging systems and processes are known and described in the art. Among these various processes are migration imaging and ionographic imaging processes.
For example, U.S. Pat. No. 3,967,959 to Goffe et al. describes a migration imaging system and process. In the migration imaging process, a migration imaging member comprising a substrate, a softenable layer of migration marking material and an overlayer is electrically charged in an imagewise configuration prior to development of the image. The migration imaging member may be electrically charged by various means, including charging or sensitizing through a mask or stencil, shape electrodes, electron beam and numerous other techniques.
An example of an ionographic imaging system is disclosed in U.S. Pat. No. 5,073,434 to Frank et al. In the described ionographic imaging system, an electrostatic latent image is formed on a dielectric imaging member by various techniques such as by an ion stream, stylus, shaped electrode and the like. The electrostatic latent image is then developed by applying electrostatically charged marking particles to the imaging member, and transferring the marking particles to a substrate such as paper. In the ionographic imaging process, the imaging member is first charged by a charging apparatus, such as a corona discharge apparatus, to a uniform electrostatic charge, after which the imaging member is exposed in an imagewise fashion to selectively discharge the imaging member to form an electrostatic latent image. In the described process, the charging apparatus comprises a single corona discharge unit.
In the conventional printing and imaging processes, the imaging member is generally charged to a high electric potential, on the order of 1,000 volts, by a single charging unit. A benefit of precharging the imaging member to a high potential is to avoid problems associated with lower potentials being created on the imaging member surface by triboelectrification against components such as the cleaning blade and developer that are in contact with the surface of the imaging member. For example, triboelectric charging levels on the imaging member may reach levels near 600 volts in either polarity, depending on the imaging member thickness and on the materials chosen for the contacting subsystems. By choosing the precharge level higher than the highest triboelectric charge level, all image areas and triboelectric charge areas may be precharged to a uniform level by the precharging device.
However, a problem with conventional charging devices has been the phenomenon of edge deletion, which occurs at positions of the imaging member that are not adequately precharged to the desired high potential. A further problem with the conventional charging devices is the difficulty in providing linear charging devices of varying lengths.